netdev - Re: [patch 27/28] Introduce U16_MAX and U32

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Message-ID: <alpine.LFD.0.999.0708132039200.29609@enigma.security.iitk.ac.in>
Date:	Mon, 13 Aug 2007 20:59:09 +0530 (IST)
From:	Satyam Sharma <satyam@...radead.org>
To:	David Miller <davem@...emloft.net>
cc:	akpm@...ux-foundation.org, netdev@...r.kernel.org
Subject: Re: [patch 27/28] Introduce U16_MAX and U32_MAX

Hi David,

On Fri, 10 Aug 2007, David Miller wrote:

> From: akpm@...ux-foundation.org
> Date: Fri, 10 Aug 2007 14:12:10 -0700
> 
> > From: Satyam Sharma <satyam@...radead.org>
> > 
> > ... in kernel.h and clean up home-grown macros elsewhere in the tree.
> > 
> > Leave out the one in reiserfs_fs.h as it is in the userspace-visible part
> > of that header. Still, #undef the (equivalent) kernel version there to
> > avoid seeing "redefined, previous definition was here" gcc warnings.
> > 
> > [akpm@...ux-foundation.org: fix U16_MAX, U32_MAX defns]
> > Signed-off-by: Satyam Sharma <satyam@...radead.org>
> > Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> 
> I won't apply this one, for two reasons:
> 
> 1) The reiserfs definition is better, it is _type_ based.
>    Please use (~(__u16)0) and (~(__u32)0), respectively.

Hmm, in that case ((__u16)0xffff) and ((__u32)0xffffffff) are probably
better and clearer -- as that's what u16_max and u32_max are, after all.

We do require the (~0) thing for the max int/uint/long types, but that's
because those are types where the number-of-bits is not known when writing
the macro definition -- but that's not case with u16 and u32, so the
0xff... variants are clearer, IMHO.

> 2) The reiserfs definition is going to define an equivalent
>    value, so just adding an #undef and still letting reiserfs
>    override is wrong.  Why put a common define in kernel.h
>    if other headers still keep their own crufty copy too?

Because removing the (re-)definition of U32_MAX from in there in
reiserfs_fs.h will break builds of all userspace users of U32_MAX and
max_reiserfs_offset(), would it not? I haven't looked at any reiserfs
userspace tools source code, so possibly none such (that use
max_reiserfs_offset) exist, but I thought it better to be safe.
I'll have a look at the reiserfs-utils package, just in case.

Thanks,
Satyam
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